1. FIELD OF THE INVENTION
This invention relates to a linkage assembly adapted to be incorporated in a gear shift control lever assembly for the transmission of a motor vehicle.
2. DESCRIPTION OF THE PRIOR ART
A linkage assembly of the type used in a transmission gear shift control lever assembly transmits motion input to a gear shift lever by an operator to shifting levers pivotally attached to the outer housing of a transmission. The shifting levers drive shift forks which move synchronizers mounted on rotating shafts into and out of contact with gears in the transmission to thereby change the gear ratio output by the transmission. Linkage assemblies used in gear shift control lever assemblies must be adjustable and must be capable of maintaining an adjustment setting for a prolonged period of time.
One prior adjustable linkage assembly incorporates a pair of spaced trunnions. The assembly may be adjusted to change the spacing between the trunnions. This assembly consists of a rod having one end bent 90 degrees. A trunnion is machined onto the end that has been bent to provide a first trunnion which extends laterally with respect to the longitudinal axis of the rod. A flat is machined along the outer surface of the longitudinally extending portion of the rod to cause the rod to have a D-shaped outer surface. A second trunnion is mounted in a clamp adapted to be mounted on the longitudinally extending portion of the rod. The clamp includes a U-shaped steel stamping having a pair of aligned D-shaped holes which complement the outer surface of the rod. An anchor bolt is received within a tapped hole in the clamp to rigidly anchor the clamp. The trunnion is mounted in the clamp such that it projects laterally from the longitudinally extending rod and 180 degrees from the direction of the first trunnion when the clamp is mounted on the rod. The threaded bore which receives the tightening bolt is laterally aligned with the flat formed on the rod such that the tightening bolt bears against the flat to anchor the second trunnion at a desired distance from the first trunnion.
One disadvantage of this assembly relates to its cost inasmuch as the rod requires extensive machining to form a trunnion at one end and to provide a D-shaped cross section on the outer surface thereof. Additionally, it has been found difficult to precisely form the "D" shaped holes in the clamp and to mount a trunnion on the clamp with the precision required to provide precise orientation of the two trunnions with respect to each other.
Accordingly, it is desirable to provide a linkage assembly having a pair of trunnions which requires minimal machining and is relatively inexpensive to manufacture, which allows precise orientation of the trunnions with respect to each other, which may be adjusted easily and which will hold an adjustment once it has been set.